Grab a substring out of a string with Perl. But: Perl is the road to hell. Don't do it, mon.

perl-re-capture.sh

cat edWebLog.txt | perl -e 'while (<>) { /caching service background update finished on thread  \(id 21\) in ([0-9]+) ms/ && print "$1\n";}'

# Simpler:

echo abc | perl -n -e '/a(.)c/ && print "$1\n";'

# So, the first line becomes:

cat edWebLog.txt | perl -n -e '/caching service background update finished .* in ([0-9]+) ms/ && print "$1\n";'

# Note that the UNESCAPED parens are the capturing group.  The escaped parens are just literal parens in the regex.